Veterinary Services

Pregnancy toxaemia was diagnosed in a group of housed ewes from the Edinburgh area that were presented to a local practitioner with nervous signs evident in a few individuals.  Although a history of lead paint use had been identified in the shed blood lead measured in two of the affected animals was insignificant.  In contrast beta-hydroxybutyrate concentrations were very high in one and moderately elevated in the other (7.2 and 1.6 mmol/l respectively, reference range ≤ 1.2 mmol/l).

Toxic conditions 

 
A problem with a milk replacer that contained excessive vitamin A levels was investigated at St Boswells. Two March born lambs from a group of 18 being reared artificially were submitted alive for necropsy.  Both lambs demonstrated a stiff gait and had skin lesions around the eyes and muzzle, and on the medial hock and elbow joints.  A number of similar cases had been reported by colleagues in AHVLA and in those outbreaks disease had been associated with abnormally high concentrations of vitamin A within the milk powder that was being used.  In this case, although serum vitamin A was found to be within normal limits, liver concentrations of the vitamin were greatly elevated.  Further enquiries at the farm in question revealed that the remaining lambs in this group had suffered a severe growth check and had been euthanased.

Generalised and systemic conditions

Maedi visna infection was suspected to be responsible for large numbers of very lean ewes after lambing in a large upland commercial flock in the Borders.  On blood sampling a batch of 20 ewes, 16 were found to be seropositive to maedi visna.   A maedi visna breakdown was known to have occurred in an adjacent pedigree flock and SACCVS suspected that poor fencing may have allowed contact with this commercial flock.  Advice was given to the commercial flock owner regarding the management and control of the disease.

Alimentary tract disorders

Seven outbreaks of lamb dysentery due to Clostridium perfringens Type B were diagnosed by SAC C VS during April, the same monthly total as last year.  Unusually however, outbreaks reported by Perth, Ayr and Edinburgh all occurred in flocks where a programme of maternal clostridial vaccination was in place.  In each case the diagnosis of lamb dysentery was suspected based upon a history of haemorrhagic scouring and deaths amongst lambs between two and four weeks of age.  The diagnosis was confirmed on gross postmortem findings of haemorrhagic enteritis and the detection of the beta and epsilon toxins of Clostridium perfringens within gut contents.  At Edinburgh additional histopathology was performed and this revealed necrotising enteritis with Gram positive bacilli with the appearance of Clostridium species coating the denuded villi.  Where disease outbreaks occur in the face of immunisation possible explanations include an inadequate vaccination programme, poor colostrum consumption by the lambs or the involvement of a concurrent infection. 

Intestinal perforation was reposnible for the death of three recently-lambed gimmers shortly after turnout in a lowland flock near Edinburgh. On-farm postmortem examination of two of the carcases by the local practitioner revealed perforated small intestines with intestinal content free in the peritoneal cavity.  The third gimmer was submitted to Edinburgh. At necropsy a small quantity of intestinal content was present throughout the abdomen, but with no gross inflammation or fibrin exudation.  There were two diagonally-opposed holes in the duodenum 12cm distal to the pylorus.  In addition the liver was small and irregular with fibrosis evident.  Histopathology revealed a dramatic acute peritonitis with coagulative necrosis of the duodenal mucosa, and also lesions of chronic fasciolosis.  A diagnosis of embolism of the gastroduodenal artery with infarction and perforation of the duodenum was made, along with intercurrent fasciolosis.  While intestinal perforation is recognised as an occasional event, no explanation was found for the three associated cases.

Respiratory tract conditions

Pneumonia due to infection with Mannheimia haemolytica was confirmed on examination of viscera submitted to Aberdeen from a mule gimmer found dead two days after lambing. Two other gimmers in the flock were showing signs of respiratory disease. The appearance of the lungs submitted was suggestive of atypical pneumonia with involvement of Mycoplasma ovipneumoniae.

Reproductive tract conditions

Foetopathy due to border disease was diagnosed in two Renfrewshire flocks, bringing the total for this year to eight and twice the number for the same period in 2010.  The diagnosis was made in one flock following examination of a recumbent lamb with an evident head tremor. This condition was initially thought to be swayback and a total of twelve similarly affected lambs were reported by the flockmaster.  However border disease was confirmed when suggestive neuropathological changes were noted and specific immunolabelling for pestivirus in the brain gave a positive result.  The same diagnosis was made serologically in a second Renfrewshire flock in which two ewes had produced “hairy shaker” lambs.

Musculo-Skeletal conditions

A joint-ill problem affecting 20 lambs on a Scottish Borders unit was found to be associated with Streptococcus dysgalactiae infection.  This has been the only confirmed case of this condition thus far in 2011, although in previous years the diagnosis has been recorded in 20 or more flocks by the end of April.  A marked annual variation in the incidence of this condition has been noted in the past but remains poorly understood. 

Nervous system disorders

A spinal abscess thought to be due to tick pyaemia was the cause of posterior paralysis in a four-week-old lamb examined at Aberdeen, one of several similarly affected in the flock.  Staphylococcus aureus was isolated from the abscess.  Although, no ticks were found on the lamb an abscess in the left axilla was suspected to be due to previous tick attachment.

Skin diseases

Mycoplasma conjunctivae was identified by PCR in a case of conjunctivitis. A flock comprising 20 sheep was repeatedly on antimicrobial treatment after the eye infection had left multiple animals blind. The condition had reportedly responded well to treatment, but repeatedly reappeared over a period of three months as soon as the effect of the treatment wore off.